An Experimental Investigation on the Convective Heat Transfer Coefficient and Nusselt Number in Water/Carbon Nanofluid

The heat transfer coefficient of a fluid is one of the most important effective factors on the performance of a fluid in the heat transfer process. Due to the higher conductive heat transfer coefficient of metals than liquids, metal particles can be used to increase the heat transfer rate of liquids. Nano fluid is one of the novel and developing methods to improve heat transfer rate in heat exchangers. In this paper, the main effective parameters on increasing the convective heat transfer coefficient of carbon nano fluid compared to water as based fluid, including: flow rate and concentration, in the range of 7100 to 16700 for Reynolds which is known as turbulent flow, are investigated. The results illustrate that increasing in Re number leads to increase the Nusselt number and convective heat transfer coefficient, and moreover decrease the friction factor. It is also showed that in a constant Re, carbon nano fluid has been able to create up to 10.17% more convective heat transfer coefficient, compared with pure water as base fluid. It was found that adding Carbon nano-particles to water, initially leads to increase in the convective heat transfer coefficient of the nanofluid. This increase continues to a concentration of about 0.2 wt% of the nano-carbon, and then has a descending trend. In addition, the pressure drop due to changes in Re, was investigated too, and showed that the behavior of this curve is in agreement with Moody’s diagram.